I can't make it, but let me help you out with a little info.
Atwater beach is just north of Milwaukee in the town of Shorewood- at the end of Capitol Drive.
There is some parking there and they may, or may not, charge you to enter the beach area- it changes all the time depending upon who is working.
You can see the stairway that you need to walk down, which is much nicer than the path that used to be there 20 years ago! Once you get down to the beach you'll notice three large jetties, look at the picture, and a very small steel pier just to the north.
IF you want to dive the Josephine, 100' long set of rubs and a keel in less than 10' of water, walk up to the little steel pier and take a 90 degree compass heading straight out- you can probably see some of it if you stand on the end of the pier.
If you want to dive the much bigger wreck, Appomattox, you'll need to take a 60 degree compass heading off of the large jetty that is furthest to the north- left hand side of the beach.
On scuba it's about 400 kick cycles, but if you freediving it you can just snorkel out until you see it. That wreck lies in 18'-23' of water and comes up off the bottom a good 6'-8'. She's over 300' long and at least 60' wide. I have seen salmon and other big fish swim into this area on past dives. I believe that it is now marked with a state buoy.
Have fun!
Jon